This invention relates generally to determination of the level of dissolved carbon dioxide in liquids. More specifically, it pertains to apparatus and a method for continuous analysis of the amount of dissolved CO.sub.2 in beverages or other liquids during a bottling process, and is particularly suited for "on-line" application, as for example, in analyzing wine or beer supplied from the line feeding bottle filler apparatus.
It has been recognized that it is exceedingly difficult to obtain consistent and accurate measurements of CO.sub.2 in beverages during bottling because of the inherent unpredictability of CO.sub.2 when subjected to the conditions of known analyzing techniques. However, accurate determination of CO.sub.2 content is of importance for maintenance of product quality and satisfaction of Federal regulations applicable to consumed liquids.
One prior technique employed in analyzing wine, for example, relies upon diffusion of CO.sub.2 through a semi-permeable membrane tapped into the wine line. The diffused gas is introduced into a nitrogen stream which is then fed at a constant flow rate to an infrared analyzer adapted for determining relative CO.sub.2 concentration. The technique suffers the drawback of yielding only a relative rather than a quantitative reading. It is further deficient as providing non-uniform results since variations in alcoholic content, dissolved solids in the wine, temperature, membrane permeability, interruptions in the bottle-filling operation and other factors affect the readings obtained.
Heretofore, the procedures employed in analyzing CO.sub.2 in beverages such as wines, as standardized by the Association of Official Analytic Chemists, and set forth in Official Methods of Analysis (1970) 11th. Ed., A.O.A.C., have mainly been directed to time-comsuming manual techniques which have provided less than desirably accurate and reproducible results and do not present a continuous reading. These techniques do not satisfy the need for a continuous analyzing method for maintaining a uniform level of CO.sub.2 in wines and other beverages bottled at high speeds. Of the best known manual methods, the manometric method (AOAC 11.053-11.057) and volumetric method (AOAC 11.058-11.060) are particularly time-consuming, and the enzymatic method (AOAC 11.061-11.062), while somewhat quicker, is frequently found to be an inconveniently difficult procedure. All these methods require rigorous sample preparation and meticulous manipulations with chemical reagents. Recent proposals for analysis of CO.sub.2 in wines have been concerned with modifications and improvements of the various manual techniques, recognizing their shortcomings.